The Newtonville and Watertown Street Railway was leased October 1, 1897, allowing it to continue northeast to Watertown. An extension southwest to Needham center was built in 1906. On October 9, 1909, the Newton and Boston was merged into the Middlesex and Boston Street Railway.

The line was bustituted in 1926. The Massachusetts Bay Transportation Authority began to subsidize the route in September 1964, and assigned it the number 32 Needham-Watertown. When the MBTA took over the M&B on June 30, 1972, it was renumbered to 532. It was again renumbered in September 1982, and is now the 59 Needham Junction - Watertown Square via Newtonville.

The only changes from the original route to the present day have been at Newton Upper Falls. The original alignment was rather circuitous, looping north of Eliot Street on High, Summer and Chestnut Streets, presumably to avoid steep grades. An alignment in the mid-1970s used a one-way pair, with the northbound direction looping south of Eliot Street. It now uses the old northbound side (Oak and Chestnut Streets) in both directions, the opposite of the original route.

Until April 1981, the route only went north from Needham Center; it was extended at that time to Needham Junction. 59A Needham Street-Watertown Square was added in December 1984, running Watertown to Newton Highlands and splitting there onto its own alignment to the Needham Industrial Park. 59A service was merged into 59 in December 1989, with alternate weekday trips using the 59A alignment (and continuing to Newton Junction).